Arc interrupter



Sept. 19, 1933.

R F3. PHTTMAN ARC IN'I'ERRUPTER Filed June 16, 190

INVENTOR Patented Sept. 19, 1933 ARC INTERRUPTER Ralph E. Pittman, PineBlufl, Ark.

Application June 16, 1932., Serial No. 617,585

4 Claims.

This invention relates particularly to discharge devices for use inconnection with overhead transmission and distribution lines, and hasfor its primary object the provision of means for posi- 5 tivelypreventing an excessive superimposed voltage rise on a conductor orconnected apparatus such as might be caused by lightning.

. Considerable difficulty has heretofore been encountered in devices ofthis character, as it is necessary that extremely high lightningcurrents be discharged through these devices, requiring a thermalcapacity generally lacking in resistance or porous materials. Inaddition the device should quickly extinguish any power are tending tofollow the lightning discharge, whether the current flowing in the arebe of very large or very small magnitude. To accomplish this resultwithout the use of moving parts requires a certain amount of resistancein series with the device, and this resistance is objectionable in thatit increases the surge voltage applied to the apparatus it is intendedto protect by the amount of the impedance drop in the resistance. Aslightning currents are now known to be of the order of tens or hundredsof thousands of amperes, it is readily apparent that even a very fewohms of resistance in the discharge path is extremely undesirable.

It is an object of this invention to provide means for interrupting withequal facility large and small current arcs by controlling the area ofthe arc path in such a manner that this area automatically adjustsitself to the magnitude of the arc current.

A further object of this invention is to provide a simple, inexpensiveand effective discharge device for the purpose above described.

With the above and other objects in view which will appear from thedescription, my invention resides in a novel construction, combinationand arrangement of parts substantially as hereinafter described and moreparticularly defined by the appended claims, it being understood thatsuch changes as come within the scope of the claims may be made in theembodiment herein disclosed.

In the drawing, Figure 1 is a side elevational view of the device in theservice position.

Figure 2 is a side elevational view of the device, shown in section.

Figure Bis-a front elevational view of the device, also shown insection.

As shown by the drawing, the housing 10 is of some suitable insulatingmaterial, as porcelain, and arranged to be supported on a crossarm 24 inany suitable manner, as by the U shaped metal bracket 21, and the bolt22 extending vertically through the crossarm 24. The U shaped member 21is rigidly attached to the housing 10 by means of the bolt 13, thelatter extending through the midpoint of the disk 14, the wall of thehousing 10, and one arm of the U shaped bracket 21. The nut 12 providesmeans for rigidly clamping this assembly together. w

A second disk 15 is supported coaxially with and biased against the disk14 by the coil spring 16. Circular grooves for seating the spring 16 areprovided in the disk 15. and the wall of the housing 10.

A flat metal member 17, having its end portions 0 bent at right anglesto the principal axis of the member is rigidly secured ;to the housing10 by the bolt 19 extending through both the housing and one of the bentend portions.

The bolt 19 also provides means for attaching a line wire 20 thereto,and in a similar manner the nut on the bolt 13 provides means forattaching a ground wire thereto.

The disks 14 and 15 are preferably made of some insulating material noteasily affected by heat or shock, and I have found such a material ashorn fiber an inexpensive and effective material.

The bent member 17, having the line wire 20 attached thereto, becomesthe line electrode of the device, and similarly, the bolt 13, having theground wire 11 attached thereto, becomes the ground electrode of thedevice.

In operation, any voltage appearing on the electrode 17 of a characterto break down the spark gap formed by the line electrode 17 and theground electrode 13 will follow a path between the disks 14 and 15rather than puncture the solid insulation of the disks. This'path ispurposely made the weakest electrical path through the device, so thatthe initial discharge always occurs along a radius between the disks 14and 15 from the line electrode 17 to the ground electrode 13.

A power are immediately follows the spark or arc caused by thesuperimposed voltage, but is immediately extinguished by its confinementbetween the disks 14 and 15. In the case of small power currents, thereis relatively little movement of the movable disk 15. With largecurrents through the device, there is quite an appreciable movement, butit will be seen that the spring 16 is continually biasing the disk 15against the disk 14, with the arc therebetween. Since in an 1alternating current circuit the magnitude of the current is zero twiceeach cycle, the movement of the disk 15 into the arc path is relativelyunopposed at the instant of zero current. The are path is thus replacedby the dielectric of the disk 15 at such a period, raising the voltagenecessary to maintain the arc above the normal line to ground value, andthe arc is in this manner extinguished within the first half-cyclefollowing the initial break down.

It will be apparent that sheets of insulating material having shapesother than disks may be used as long as the shortest path between thedisks is from an outside edge to a central electrode. It is quiteimportant that a central electrode be used, otherwise an alternate pathmay be established in air around the preferred gap,

resulting in failure to properly operate.

I have found that horn fiber disks of such a diameter that the arc pathis only 3 /2", with a bias of 12 lbs., will efiectively interrupt 8,000

volt arcs to ground. I have also found that a disk 2" in diameter,making an arc path from central electrode to periphery of 1", .willeffectively interrupt 2300 volt arcs.

The device may also be used with disks of other insulating material thanfiber. Marble disks require a slightly longer are path, or about 1 forinterrupting a 2300 volt are.

It will be apparent that the variable area of the arc path, ascontrolled by the effect of the arc itself opposing the bias of thespring 16, makes the device independent of the efiective current value,as with the larger currents the disks separate to relieve the internalpressure, while at current zero there is present little pressure tooppose the bias of the spring 16.

Since the venting action of the device is entirely controlled by theinternal pressure, both the discharge and interrupting capacity areextremely high, and the cost of the device for extremely high currentsis relatively low.

Other embodiments of the invention herein described will readily appearfrom this description. One such embodiment might employ a plurality ofinsulating disks, the central electrode extending therethrough, and theouter electrode extending along the edge of the disks. Such aconstruction might be desirable for unusually high currents, but Iprefer for reasons of economy and simplicity, to use two disks wherepossible.

From the foregoing description taken in connection with the accompanyingdrawing, it will be apparent to those skilled in the art that I providea novel and improved arc interrupter for the purpose described.

What I claim as my invention is:

1. In an arc interrupter adapted to be interposed between a line andground, a pair of coaxial disks of insulating material, a groundelectrode positioned adjacent the center point of one of said disks, aline electrode positioned adjacent the periphery of said disk, saidelectrodes forming a spark path along a radius of said disks andtherebetween, and a spring for biasing one of said disks axially to theother.

2. An arc interrupter comprising a housing of insulating materialforming a support for a pair of fiat sheets of insulating material, afirst electrode extending through adjacent the central point thereof andrigidly supporting one of said sheets within said housing, a secondelectrode positioned adjacent the periphery of said sheets to form aspark path between said pair of sheets from the first electrode to thesecond electrode, and.a spring supporting and biasing the other of saidsheets against the rigidly mounted sheet whereby the action of an arcbetween said electrodes tending to increase the opening between saidsheets is opposed by the deformation of said spring.

3. An arc interrupter comprising in combination, a fixed sheet ofinsulating material having a first electrode adjacent the mid-pointthereof, a movable sheet of insulating material of substantially thesame dimensions as said fixed sheet resiliently biased toward said fixedsheet, and a second electrode positioned at a point adjacent the outeredge of said sheets.

4. An arc interrupter comprising, in combination, a stack of fiat sheetsof insulating material, a first electrode extending into stack normal tothe plane of said sheets adjacent the mid point thereof, a secondelectrode parallel to said first electrode adjacent the outer edge ofsaid stack, said electrodes forming a spark path between said sheets,and means including a spring for resiliently biasing said sheetstogether.

RALPH R. PI'I'I'MAN.

